The invention relates to a process for producing a sliding body of a ceramic material, in particular of Si/SiC, for sliding systems, in particular for slip-ring seals.
Axial and radial slip-ring seals are used, as a rule, to seal rotating machine parts against liquid or gaseous media and generally have a stationary and a rotating slip ring which are pressed against each other by a spring element. The slip rings form a sealing gap in which the slip ring surfaces are arranged opposite each other. When the seal is in operation, the sealing gap contains a liquid sealing agent in which there is a drop in pressure. For difficult sealing cases, for example in machines in which there is a very high or very low internal pressure, use may be made, for example, of axial slip-ring seals which ensure a hydrostatic and hydrodynamic seal and at the same time relieve the slip-ring seal of load. This is achieved by introducing so-called hydrodynamizing recesses into the slip ring (German Auslegeschrift 1,475,621 and DE-B 2,928,504). At high pressures and temperatures, particular measures are necessary to cool the slip rings. In this connection it is known to provide coolant channels in the slip-ring bodies through which a coolant flows (CH-B 413,522). In the case of ceramic slip-ring seals, in particular, it is very difficult and expensive and only possible with considerable complexity to introduce both hydrodynamizing recesses and also coolant channels. It has been possible to solve this problem by constructing the ceramic slip ring with complicated internal structures composed of individual so-called "green films" into which the required channels, holes, recesses etc., have already been introduced, for example, by punching out and then firing the laminated slip ring in a known manner to produce compact bodies. Such a process is described, for example, in EP-A-0,092,716. However, this process has disadvantages, in particular if a sliding body is assembled from a solid parent body and a part produced by "film technique" and is fired to form a finished body. At the lamination point between the solid parent body and "film body", a weak point at which the sliding body may break apart during subsequent use or, if SiC is used, even during siliconizing, is produced owing to the non-ideal sintering together of the two parts. This is apparently attributable to the fact that the ceramic compounds for the two parts are prepared in different ways and that, for example, the proportion of organic constituents in the film body is greater than in the solid parent body which is generally dry-pressed.